Mainspring for watches



(No Model.)

No. 448,191. Patented Mar. 10,1891.

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UNITED STATES Patient @rricn.

ERN CST MAX FASOLDT, OF ALBANY, NFAV YORK.

MAINSPRING FOR WATCHES.

SPECIFICATION forming part of Letters Patent No. 448,191, dated March 10, 1891.

Application filed September 12, 1885. Period No.1'76,858. (No model.)

To ctZZ whom it 11mg concern:

Be it. known that. I, ERNEST MAX Fitsonorr, of the city and county of Albany, in the State of New York, have invented new and useful Improvements in \Vatches and other Time- Pieces, of which the following is a specification.

My invention relates to an improvement on mainsprings of watches, clocks, and other springactnated apparatus; and the object of my invention is to prevent the breaking of the mainspring and damaging the connected mechanism by .reason of an overwinding of said mainspring; and to attain this object my invention consists in connecting the outer end of the mainspring to an auxiliary spring or friction-spring in such manner that an overwinding of said inainspring will cause the friction-spring to be pushed endwise in the direction toward which the unattached end of the latter points, whereby a sufficient expansion of the coil of said friction-spring is obtained to produce ample frictional contact between said friction-spring and the bore of the spring-barrel which contains said springs to obtain the required degree of resistance to the slipping of said frictionspring to allow said mainspring to be wound up to the limit of safety, and when said limit has been attained said friction-spring will slip over the surface of the bore of the springbarrel without increasing the tension of the mainspring, said friction-spring having a length that exceeds the circumference of the bore of the spring-barrel by at least oneeighth of said circumference, and the free or unattached end of said friction-spring being arranged to lie between the opposite end of said spring and the face of the bore of the spring-barrel, so that the expansion of said friction-spring produced by the winding up of the mainspring will create a pressure to grip the unattached end of the friction-spring between the attached end of the latter and the bore of the spring-barrel, the frictional resistance thereby attained being sufficient to allow the mainspring to be wound up to the limit of safety, but permitting said frictionspring to slip when that limit has been attained.

My invention is especially adapted to that class of watches like the present style of American watches-from which the stopwork is omitted.

In the accon'ipanying drawings, which are ierein referred to and form part of this specification, Figure 1 is a magnified plan View of the spring-barrel of a watch uncovered and showing the mainspring in an unwound condition. Fig. 2 is a like view, showing the niainspring wound up. Figs. and a are respectively a side elevation and an edge view of the friction-spring detached, and Fig. 5 is a detail showing a modification of the mode of connecting the outer end of the mainspringwith the friction-spring.

As represented in the drawings, A is the spring-barrel of a watch; 13, the arbor to which the inner end of the mainspring is attached; C, the mainspring, and D the friction-spring, which forn'is an auxiliary to the mainspring.

The spring-barrel A is made in the usual form of such devices, cxceptingthat the hook or catch to which the outer end of the mainspring is usually attached is dispensed with. The arbor ii is made in the usual form and is provided with a hook or stud Z) for attaching the inner end of the inainspring thereto. The mainspring C is also made in the usual manner, and,as 1 preferably make them, with the usual hole near ends thereof. The hole near the inner end of the coiled spring is fitted to engage on the hook Z) of the arbor, and the hole near the outer end of said mainspring is fitted to engagein like manner with a hook or stud on the friction-spring. The friction-spring D consists of a piece having about the same cross-sectional areaas the niainspring and possessing about the same degree of elasticity. The length of said fric- Lion-spring should be equal to about one and one-eighth times the circumference of the bore of the springbarrel, so that the free end of said spring will overlap the opposite or attached end thereof to that degree, the overlapping end being arranged to lie between the attached end and the bore of the spring-barrel. Said friction-spring when made as shown in Figs. 3 and 4: is provided near one end with a hook or stud d, which inclines toward the nearest end of said spring, and which is fitted to engage in a hole in the outer end of the mainspring. The connection between said friction-spring and mainspring is made in such manner that the winding up of the mainspring will tend to move the frictionspring D endwise, in the direction indicated by the arrow in Fig. 2-that is to say, to push it endwise in the direction toward which the free end of said friction-spring is turned,and by this pushing endwise pressure the coils of said friction-spring will be expanded to increase the friction of said friction-spring with the bore of the spring-barrel A; but I find by experience that the resistance produced by this frictional contact, while it suffices to permit the winding up of the mainspring, is in sufficient to resist any act of overwinding, whereby the mainspring will be brokenor damaged, for the reason that when the friction-spring is made and arranged as herein set forth said friction-spring will slip on the surface of the bore of the spring-barrel. I find by experience that by giving the friction-spring a length that exceeds the circu n1- ference of the bore of the spring-barrel by about one-fifth of said circumference, when mainsprings of ordinary strength are used, the best results are produced. By shortening the overlap of said friction-spring the frictional adhesion of said spring with the bore of the spring-barrel is lessened in a pr0- port-ionate degree, and an overlap of less than one-eighth of the circumference of the bore of the spring-barrel will not create sufficient frictional adhesion of the friction-spring to obtain more than a partial winding up of the mainspring, and by lengthening the overlap to about one-third of the circumference of the bore of the spring-barrel so great a degree of frictional adhesion can be produced as to prevent the friction-spring from slipping around in the spring-barrel, and thereby the usefulness of my invention, so far as it relates to the prevention of breaking the mainsprings, would be practically destroyed.

Inthe modification shown in Fig. 5 the hook (1 (shown in Figs. 3 and 4) is dispensed with and the connection of the mainspring (3 with the friction-spring D is formed by turning back the outer end of the mainspring to form a hook c, which will engage over the end of the friction-spring D, as shown in Fig. 5. By this modification I provide means for connecting the mainspring with the frictionspring when the hook d is broken off or has been omitted from the latter.

When preferred, the mainspring O and friction-spring D may be permanently connected together either by riveting or soldering, or the two may be made in one piece by bending the part for the friction-spring backward 011 the outer coil of the mainspring, and my invention includes such a modification.

The operation of my invention is as follows: The friction-spring D, made in such length that it will exceed the circumference of the bore of the spring-barrel about onefifth of said circumference, the overlapping end being fixed between the outer coil ofsaid spring and the bore of said spring-barrel, and said friction-springbeingattached to themainspring in such relation that the operation of winding up said mainspring will tend to push the friction-spring endwise in the direction toward which its free end is turned, whereby sufficient enlargement of the diameter of the coil of said friction-spring is produced to create an increase in the frictional adhesion of the latter with the bore of the spring-barrel that will prevent said friction-spring from slipping until the mainspring is fully wound up, the mainspring is then wound upin the usual manner to the full extent of the tensionthat is to say, as far as it can be wound without endangering its safetyand when this point is attained the friction-spring D will slip in the bore of the spring-barrel without increasing the strain on the mainspring.

I am aware that friction-springs have l'eretofore been used auxiliary to mainsprings, in some instances being attached to the mainspring, so that said friction-spring would be pushed endwise in the direction to which its free end was turned; but such frictionsprings were of less length than the circumference of the spring-barrel. In other cases the friction-spring was attached to the mainspring in such manner that said frictionspring would be drawn instead of being pushed around in the bore of the spring-barrel, and thereby the tendency to increase the diameter of the coil of the friction-spring was entirely destroyed.

I do not claim these earlier constructions;

but

hat I claim as my invention, and desire to secure by Letters Patent, is-

The combination of a spring-barrel and its arbor and a mainspring having attached to its Outer end a friction-spring whose length is at least one and one-eighth times thecircumference of the barrel, the Overlapping end of said friction-spring being retained and pressed between the coil of the latter and the interior of the barrel, substantially as described.

E. MAX FASOLDT.

Witnesses:

WM. H. LOW, S. B. BREWER.

all .4

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